BRCA1
and
BRCA2
the first two major genes found to be associated with susceptibility to breast and ovarian cancer. Cloned respectively in 1994 and 1995, BRCA1 and BRCA2 were the first major cancer genes for which widespread genetic testing was done; within several years, direct screening became available. The risk of breast cancer in women with mutations in one of these genes ranges from 56% to 85%, and this type of breast cancer tends to occur at a younger age than do most other types. Risk of ovarian cancer is also greatly increased. BRCA2 mutations are also associated with increased rates of male breast cancer, although these rates remain low (around 1% of all breast cancers). Because of incomplete penetrance of these genes, a small percentage of mutation carriers never develop breast, ovarian, or associated cancers. See also risk perception.